1. Field of the Invention
The present invention pertains to a color image reading apparatus and a color image reading method to read color images, and more particularly, to a color image reading apparatus and a color image reading method in which scanning speed can be changed.
2. Description of the Related Art
In recent years, color image reading apparatuses that scan the image of an original document to read a color image and that can change speed of said scanning have been developed. The apparatuses are made capable of changing the scanning speed in order to meet mutually incompatible demands, i.e., to obtain a desired image quality and to improve the efficiency of the image input operation.
For example, where an extremely fine image is to be input, the scanning speed is set to be slow (image quality priority mode) to improve the reproducibility of fine lines. On the other hand, where a simple image for which fine line reproducibility is not an issue is input, the scanning speed is set to be fast (speed priority mode) to improve image input operation efficiency.
When the scanning speed is changed in this way, the amount of light received by the sensor changes from one speed to another, and the signal level (image data value) output from the sensor also changes. Therefore, the sensor output is corrected such that it becomes constant regardless of whether the scanning speed is set to slow or to fast.
However, in a conventional color image reading apparatus of this type, only the output correction mentioned above is performed based on the scanning speed, and therefore, a problem arises in the color reproducibility of the color image.
In other words, the problem arises that, when identical color masking conversion is carried out for images scanned using different speeds, a discrepancy or color imbalance occurs between the colors of the image read and the colors of the printed image, reducing the color reproducibility.